1. Field of the Invention
The present invention relates to a treatment unit, for example, an etching unit, spattering unit or CVD unit, and more particularly to a temperature control apparatus for controlling the temperature of a support for a substance to be treated, such as a semiconductor wafer.
2. Brief Description of the Related Art
In the treatment of semiconductor wafers, temperature plays an important role as a conditional factor for treating semiconductor wafers. For instance, in the case of a reactive ion etching (RIE) treatment, it has been known that the anisotropy of etching is improved if a semiconductor wafer is cooled down to -100.degree. C. or less. In a conventional RIE unit, there has therefore been previously developed a means of introducing a liquefied gas, such as liquid nitrogen, to a liquid reservoir in a support for a semiconductor wafer, i.e., a susceptor assembly, to cool down the semiconductor wafer. See, for example, Japanese Patent Application Laid-open (KOKAI) No. 216,076/1994.
The prior art treatment units, however, perform only a single temperature treatment in each unit. Temperature control in prior art treatment units therefore has not been performed with large variations in the treatment temperature. The prior art treatment units thus have taken long periods of time to continuously carry out different kinds of heat treatments in one treatment unit.
It is therefore an object of the present invention to provide a treatment unit which overcomes the deficiencies in the prior art by providing a treatment unit which is capable of quickly controlling the temperature of the treatment unit over